Advanced M52 Microprocessor User's Guide
ADVANCED M52UMCT2019 COLOR 9
Once the cooling demand reaches 51-99% range the unit will operate with one circuit in Free Cooling
and the opposite circuit in DX Cooling. If the cooling demand reaches 100% then the unit will switch
to DX cooling only.
When the glycol or outside air temperature drops below 7.2C (45F adjustable) the compressors will
stop automatically. The unit will operate in Free Cooling mode only at this time. The glycol or outside
air temperature is monitored by the unit using Temp EGT/ Ambient input. Temp Return Air and Temp
EGT/ Ambient can be viewed in the Settings Tab on page one. If the Glycol or Outside Air
Temperature drops below 0C, (32F) the unit will switch to DX cooling only as this too low of a
Glycol fluid or outside air temperature would cause any condensation on the evaporator coil to freeze.
Note: The Status screen on the controller indicates full free cooling is on when it displays 2/2 and will
display 1/1 in combination with DX cooling. Free cooling is off when it displays 0/2 or 0/1 under the
percentage demand next to the Free Cooling icon. The percentage of free cooling in 2/2 will show
double what the main cooling bar is showing. This percentage is reflective of the % that each valve is
open.
Reheat:
On demand for reheat the demand signal ramps up and heater contactor closes at 33% demand. SCR
or Hot Water/ Steam Reheat Valve modulates from 33% to 100% output to match the demand signal.
Once demand has been satisfied the SCR or Hot Water/ Steam Reheat Valve modulates down to 0%
and the heater contactor opens. On Multi-stage heaters each stage will be energized at equal intervals
as the demand increases from 0 to 100%. Stage 1 activates at 33%, Stage 2 activates at 66%, Stage 3
activates at 99%. When demand is met stages deactivate at Stage 3 deactivates at 66%, Stage 2
deactivates at 33% and Stage 1 deactivates at 0% heating demand.
Hot gas reheat only operates on demand for reheat during a dehumidification cycle as the demand
signal ramps up the Hot Gas reheat solenoid valve is activated at 33% reheat demand and remains
open until reheat demand decreases to 0%.
Heater stops when:
Loss of demand
Loss of air flow
Heater high temp cut out
Humidifier:
When the “On/Off/Drain “ switch is in the “On” position, a demand for humidification causes the
humidifier contactor(s) to close in stages 1 to 16, (depending on the number of units connected
together with Co-Work), as demand for humidification increases from 0 to 100%.
After a short time delay, approximately 1 to 3 minutes, the fill valve will energize allowing water to
fill the boiler bottle. The fill valve closes when the humidifier reaches its FLA current or when the
water level reaches the high water level sensor. Water begins to boil after a few minutes. The
humidifier will continue to boil and fill to maintain the humidity set point. Periodically the humidifier
will initiate a flush cycle to maintain constant steam output and to flush some of the mineral content
from the boiler bottle.
When the boiler bottle reaches the end of its useful life it will activate a Boiler Dirty Alarm and will
shut off the humidifier. It is common for the Boiler Dirty Alarm to sound on an initial start-up as the
humidifier begins the process of concentrating the mineral content of the contained water.
To drain the humidifier you must cause a humidification demand and then switch the “On/Off/ Drain”
switch to Drain. You must set the switch back to “Off “when the bottle has completely drained.
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